Just before intermission of the opening concert of the Beyond Cage Festival on October 22, I pulled out my iPhone to see if the Giants were beating the Cardinals for the National League Pennant, and was disoriented to see that it was 9:49pm. It seemed like there must have been a massive network malfunction, because the extraordinary performance of Atlas Ecpliticalis with Winter Music that I and the rest of the audience had fervently applauded could not possibly have gone on for an hour and forty-five minutes. The duration had felt assuredly like a leisurely performance of an early Romantic symphony, say the Beethoven Pastorale, something that was stimulating and enveloping but that never demanded a hint of endurance from the ear or mind.

But it was so, Petr Kotik had just led the Orchestra of the S.E.M. Ensemble, with Joe Kubera and Ursula Oppens simultaneously playing Winter Music, in almost two hours of some of the most resolutely avant-garde music, and the listening experience was such that the sensation of time was lost completely inside the performance. The extraordinary became the unbelievable.

Kotik had already presented this piece twenty years ago, in a historic concert that became a memorial to the recently deceased composer. And he and the ensemble have recorded it twice, on a recently reissued Wergo album and a great and unfortunately out of print Asphodel release, and these are not only the two finest recordings of Atlas but also two of the finest recordings of Cage’s music available. But the concert exceeded these, reflecting the understanding of such a profound work of art that can only come through time spent examining and thinking about it.

And time spent rehearsing. Kotik’s task on the podium was mainly to act as a human clock, a physically demanding but simple role. The important work went on in the rehearsals, where he worked with the ninety-something musicians, who each have a solo part in the piece, unrelated to any others. Kotik especially emphasized the importance of the players taking their time, the key component in what he pointed out in the program notes as the “first time ever” that the two pieces “have been heard together in their entirety,” completeness of forces and completeness in duration.

Atlas was heard recently at the John Cage Composer Portrait at Miller Theatre, played by ICE under Stephen Schick in a sympathetic and lively performance. But in contrast and retrospect, ICE seemed heavy on enthusiasm and light on understanding, while the S.E.M. understood this music in a profound way. Atlas is one of Cage’s greatest and most important pieces, marking a breakthrough into his mature style where he marshaled experimental techniques in the cause of beauty. Duration became increasingly important to him, as a way to allow his ideas sufficient time to play out and to limn the aesthetic of boredom. But this concert was never boring. The ensemble gave off a great sense of relaxation, the music rising and falling in activity and dynamics like a massive breath. It unfolded gorgeously through time, and the piece, and Cage’s technique, is one of the greatest examples of defining and marking time in the literature.

It is profound to hear 100 musicians play so quietly. It is profound to hear so much silence in a piece — and there were extended passages of silence. The importance of going from “4’33″” to Atlas cannot be overstated: the first is a vital thought experiment that has become an unfortunate fetish that simplifies Cage’s thought and contributions, while the second synthesizes the importance of those ideas into a moving, changing piece of music and section of time. The performance not only altered the sense of time, it also demonstrated different qualities of silence, a fluid, vibrant thing during the performance, a still and immovable thing in the pause between the last notes and the first sound of applause. It is regretful that Carnegie Hall was no more than half full, and that people fled while the music was playing, because this was an event and an experience that most likely will never be available to any of us again.

Christian Marclay’s recent Shuffle in this context came off as an encore: brief, dazzling, light-hearted and completely enjoyable. He has been collecting graphical examples of musical notation in the context of consumer objects, and has transferred them to a deck of cards that are shuffled and used to create a musical score. The guidelines for playing are as free as they come: “Play alone or with others. Invent your own rules. Sounds may be generated or simply imagined.” The result was not far different than his own music-making from LP records, with periods of exciting cacophony alternating with fragments of music that sound like bits of things that the mind almost remembers. The sharp, quick, energetic performance was the perfect thing to set us back on our feet and keep us from wandering into traffic as we left the hall.